America's 50 largest charitable donors gave away $14.7 billion last year, with Bill and Melinda Gates leading the list with a $4.8 billion donation to their foundation, according to a new report.

Giving by the top 50 donors more than doubled in 2017, soaring to $14.7 billion from $5.6 billion in 2016, according to the Philanthropy 50, compiled by the Chronicle of Philanthropy. It was the largest donation amount since 2008 — before the financial crisis put a dent in charitable giving — and it was the third-largest total ever.

The list shows that the "wealthy are flush with cash" and that the U.S. economy is strong. The report also shows that charitable giving – like wealth – is shifting toward younger tech billionaires. Ranking second on this year's charitable giving list was Facebook CEO Mark Zuckerberg and his wife Priscilla Chan, who donated $2 billion to their foundation and donor-advised fund. In third place was Michael Dell, who along with his wife Susan gave $1 billion to their foundation.

"The 2017 giving spree was fueled by huge donations from many major philanthropists who are still accumulating great wealth — and who are likely to make big gifts for years to come," according to the Chronicle of Philanthropy. "That has not been the case with previous Philanthropy 50 spikes when multiple bequests or the largesse of a single donor drove the number higher."

Some of the biggest givers last year weren't on the list, even though they wrote big checks. That's because the rankings count multiyear pledges only once, as a lump sum in the year the commitment was made. Warren Buffett, for instance, gave $2.4 billion to the Bill & Melinda Gates Foundation but didn't make the list because the donation was part of his 2006 pledge of more than $36 billion in Berkshire shares to the foundation.

Here are the Philanthropy 50's top donors, and the amounts they gave away: